Method for preparing a lactone reaction product

ABSTRACT

Method for preparing a lactone reaction product comprising reacting an alkenylsuccinic acid under substantially anhydrous conditions in the presence of a protonating agent and at an elevated temperature ranging up to about 100° C., and a motor fuel composition containing said lactone reaction product.

This application is a continuation-in-part of an application Ser. No.304,675 filed on Nov. 8, 1972, now abandoned.

BACKGROUND OF THE INVENTION FIELD OF INVENTION

The use of certain lactones or lactone reaction products as rust andcorrosion inhibitors in hydrocarbon oil compositions is known. Thus,such a material as tetrapropenylsuccinic acid lactone has exhibitedeffectiveness as a rust inhibitor in gasoline.

The alkenylsuccinic acid lactones have been prepared by reacting analkenylsuccinic acid with a hydrating mineral acid, such as 50 percentsulfuric acid, dilute hydrochloric acid or dilute sulfuric or phosphoricacid. In general, the reaction has been conducted at an elevatedtemperature ranging up to about 212° F. and in the presence of anonpolar solvent, such as hydrocarbon i.e. naphtha, kerosene or thelike. A feature of the known process is that the catalyst for thereaction has been employed in a hydrating environment, i.e. in anaqueous solution, such as 50 percent aqueous sulfuric acid or otherdilute aqueous mineral acids.

The conventional method for preparing a lactone reaction product isrelatively inefficient and produces a low yield of the desired product.In particular, the conventional method gives a poor yield of a lactonereaction product in which the alkenyl radical on the alkenylsuccinicacid reactant is a high molecular weight radical having from about 300to 3,000 average molecular weight.

DESCRIPTION OF THE PRIOR ART

U.S. Pat. No. 3,248,187 discloses a hydrocarbon oil composition whichhas been inhibited against rust by the addition thereto of a lactonereaction product. This reference discloses the process of reacting analkenylsuccinic acid in the presence of a dilute aqueous mineral acidand a hydrocarbon solvent at an elevated temperature to produce analkenyl substituted lactone reaction product.

SUMMARY OF THE INVENTION

The method of the invention which is effective for preparing arelatively high molecular weight alkenyl substituted lactone reactionproduct comprises reacting an alkenylsuccinic acid in which the alkenylradical has an average molecular weight ranging from about 300 to 3,000in the presence of a protonating agent and under substantially anhydrousreaction conditions at an elevated temperature up to about 100° C. untila substantial proportion of the alkenylsuccinic acid has been convertedto the lactone reaction product.

The motor fuel composition of the invention comprises a mixture ofhydrocarbons in the gasoline boiling range containing a minor amount ofthe lactone reaction product prepared according to this process.

SPECIFIC EMBODIMENTS OF THE INVENTION

According to the method of this invention, a high molecular weightalkenylsuccinic acid, in which the alkenyl radical has a molecularweight ranging from about 300 to 3,000, is admixed with a catalyst,electron pair acceptor or a protonating agent to form a reactionmixture. The catalyst, generally a concentrated mineral acid, can beadded next to the alkenylsuccinic acid-containing reaction mixture. Thetemperature of the reaction mixture is then raised up to about 100° C.to promote lactone formation while maintaining substantially anhydrousreaction conditions. The reaction is continued under these conditionsfor sufficient time to effect conversion of a substantial portion of thereactant to a lactone reaction product. It is convenient to follow theprocess of the reaction by withdrawing samples during the reaction andsubjecting them to infrared radiation. The formation of alkenylsubstituted 5 and 6 membered ring lactone reaction products is shown byinfrared radiation at 5.66 and 5.78 micrometer regions. Thus, byutilizing the infrared analysis or correlated reaction times, it ispossible to insure conversion of a major portion or substantially all ofthe alkenylsuccinic acid to a lactone reaction product.

The alkenylsuccinic acid reactant employed in this process isrepresented by the following formula: ##STR1## in which R represents analkenyl radical having an average molecular weight ranging from about300 to 3,000. A more preferred reactant is an alkenylsuccinic acid inwhich the alkenyl radical has an average molecular weight from about 700to 2,000. The most preferred reactants are those alkenylsuccinic acidsin which the alkenyl radical has an average molecular weight rangingfrom about 800 to 1,200.

It will be understood that the prescribed alkenylsuccinic acid reactantcan be prepared from the corresponding alkenylsuccinic anhydride.Specifically, an alkenylsuccinic anhydride and water can be reacted inequimolar amounts to form the prescribed alkenylsuccinic acid reactantin accordance with known methods. Thus, the present inventioncontemplates that an alkenylsuccinic anhydride can be employed as aprecursor to the reactant in this process by undergoing the hydrolysisreaction noted.

This process is also conveniently conducted by dissolving the prescribedalkenylsuccinic acid in an inert non-hydrating solvent such as ahydrocarbon solvent. A suitable solvent is a mineral oil having an SUSviscosity at 100° F. ranging from about 50 to about 1,000. Othersuitable hydrocarbon solvents for this process include kerosene,benzene, xylene and the like.

The interesterification reaction or formation of a lactone reactionproduct in the present invention is conducted in the presence of an acidcatalyst. The catalyst may be any protonating agent or electron pairacceptor i.e. any material which can provide a hydrogen ion or accept apair of electrons to catalyze the reaction. The protonating agent orelectron pair acceptor employed should provide from about 0.25 to 1.5moles of protons or electron acceptors per mole of the alkenylsuccinicacid being reacted although smaller or larger amounts can be employedwith compromises in efficiency and/or economy. It is preferred to employa protonating agent or electron pair acceptor which provides from about0.5 to 1 moles of proton or electron pair per mole of alkenylsuccinicacid. These ranges can be also expressed as 0.25 to 1.5 or 0.5 to 1equivalents of acid per mole of the alkenylsuccinic acid moiety.

A variety of protonating agents or electron pair acceptors can beemployed in the present process. Included among these are the mineralacids such as sulfuric acid and perchloric acid. Organic acids includingp-toluene sulfonic acid hydrate, electron pair acceptors such as borontrifluoride etherate, and solid acid catalysts such as sulfonic acid ionexchange resins are suitable. There appears to be criticality in thecatalyst since formic acid, oxalic acid and aqueous hydrochloric acidare either inoperative or have little effect on the process.

The reaction is normally conducted at a temperature ranging from about25° C. up to about 100° C. with a range from about 60° to <100° C. beingespecially suitable. A preferred temperature range for this process isfrom about 70° to 98° C. Highly efficient conversions have been realizedemploying a temperature in a preferred range, namely from about 85° to95° C. A temperature of 100° C. or above should be avoided because thesetemperatures tend to decrease conversion and lead to the production ofundesirable reaction products.

A critical feature of the process of this invention for the productionof a high molecular weight alkenyl substituted lactone reaction productis that it be conducted under substantially anhydrous conditions. Thereactant, solvent and the catalyst or the protonating agent must all beselected so as to insure substantially anhydrous and preferablyessentially anhydrous reaction conditions. By substantially anhydrousreaction conditions is meant that the reaction mixture should contain nomore than about 5 percent water. It is preferred that this mixturecontain no more than about 2 percent water with the most preferredsituation being an essentially anhydrous reaction mixture. Thesurprising improvement in yield of high molecular weight alkenylsubstituted lactone reaction product is attributed to the use of thedescribed substantially anhydrous reaction conditions.

The following example illustrates a known lactone process employing anunconventional high molecular weight polyisobutenylsuccinic acid:

EXAMPLE I POLYISOBUTENYLSUCCINIC ANHYDRIDE REACTION USING AQUEOUSMINERAL ACID

To a solution of 126 g. of a 50 wt. % oil solution of crudepolyisobutenylsuccinic acid (prepared from polyisobutene of 1300molecular weight and maleic anhydride by thermal alkenylation with about50% unreacted polyisobutene) in 125 ml. of hexane, 100 g. of 50 wt. %sulfuric acid in water was added. The mixture contained about 0.025moles of polyisobutenylsuccinic acid and about 0.5 moles of sulfuricacid or about 1.0 moles of available protons. After stirring 1 hour atabout 25° C. an aliquot is diluted with water, extracted with hexane,and the hexane extract separated. Infrared analysis of the residueobtained by evaporation of the hexane under nitrogen with mild heatingshows lactone and anhydride formation to an incomplete degree. After 4hours the temperature of the mixture was 29° C. and an infrared analysisas above showed much less anhydride and lactone formation compared tothe one-hour sample.

The mixture was then heated to reflux. The mixture temperature was about74° C. Infrared analysis after 80 minutes of refluxing (method as above)indicated small amounts of lactone and anhydride were formed, but thatthe starting material, polyisobutenylsuccinic acid was predominatelyunchanged. After 17 hours and 20 minutes of refluxing, infrared analysisindicated relatively little change in reaction mixture composition ascompared to the 80-minute reaction mixture composition.

The mixture was cooled to room temperature and washed with water andco-solvents until the wash water was about a pH of 5. The organic phasewas separated and flash evaporated. The residue was held at 95° C. atabout 20 mm Hg pressure for about 12 hours to remove solvent traces. Byinfrared analysis the final product appears to be largelypolyisobutenylicsuccinic acid with a small amount of anhydride presentand little if any lactones. The amount of lactones present cannot begreater than 15 mole % and are probably less than 5 mole %.

Upon repeating this example, no change was noted in the startingmaterial by infrared analyses at 15, 30, 60 and 90 minutes in theinitial phase (25° C.) described above and this work was discontinued.

The following examples illustrate the novel process of this invention:

EXAMPLE II

A mixture of 126 g. (0.025 mole) of crude polyisobutenylsuccinic acid(containing about 50% unreacted polyisobutene of about 1300 averagemolecular weight) in a 50 wt.% mineral oil solution and 1.25 g. (0.0125mole) of sulfuric acid is mixed at 90° C. for 3 hours. The infraredspectrum of the product indicates high conversion to five- and six-membered lactones. The yield of lactones is greater than 85 mole %.

EXAMPLE III

A mixture of 2,570 g. (1.0 mole) of crude polyisobutenyl succinicanhydride (containing about 50% unreacted polyisobutene of about 1300average molecular weight) and 25 g. (0.25 mole) of about 96% aqueoussulfuric acid and 18 g. (1.0 mole) of water were heated and stirred at90° C. for about 1 hour and then allowed to cool to room temperature.The mineral acidity can be removed by extraction but the product can beused without further purification. Infrared analysis indicates highconversion to lactones as in Example II.

EXAMPLE IV

A mixture of 1058 g. (0.5 mole) of crude polypropenylsuccinic anhydride(containing about 50% unreacted polypropene of about 850 averagemolecular weight) were heated to about 90° C. with stirring. Over aperiod of about 4 minutes, 21.5 g. of a solution consisting of 12.5 g.of about 96% sulfuric acid and 9.0 g. (0.5 mole) of water were addeddropwise. After 4 hours the mixture was allowed to cool. This producthas similar strong lactone absorptions in its infrared spectrum toExample I and give the following analysis.

    ______________________________________                                        ASTM D-94 Saponification Number                                                                        94.5                                                 ASTM D-974 Total Acid Neut. Number                                                                     55.0                                                 Iodine Number            7.8                                                  Average Molecular Weight                                                      (by vapor pressure osmometry)                                                                          955                                                  ______________________________________                                    

EXAMPLE V

A mixture of 270 g. (1.0 mole) of tetrapropenylsuccinic anhydride, 18.0g. (1.0 mole) of water, and 51.5 g. (0.5 mole) of about 96% sulfuricacid and 100 ml. of xylene were heated to reflux at atmospheric pressurefor 2 hours and allowed to cool. The product was mixed with ethyl etherand hexane and the organic phase extensively washed with water until thepH of the aqueous extract was repeatably between 4 and 5. The organicraffinate was filtered through diatomaceous earth, flash evaporated, andstripped of traces of solvent in a vacuum oven to obtain 260.1 g. ofproduct. The infrared spectrum of the product indicated high conversionto five- and six- membered lactones by strong absorptions at 5.66 and5.74 micrometers.

EXAMPLE VI

A mixture of 377.5 g. (0.05 mole) of crude polyisobutenylsuccinicanhydride (containing about 31% unreacted polyisobutene of about 400average molecular weight) 12.5 g. (0.125 mole) of about 96% sulfuricacid, and 9.0 g. (0.5 mole) of water were heated to about 90° C. withstirring for 1 hour and allowed to cool. The product was washed free ofmineral acidity by extraction and weighed 360.9 g. afterhandling-solvent evaporation. The product exhibited the same stronglactone absorptions in its infrared spectrum as the product of ExampleII.

Examples II through VI illustrate the effectiveness of the novel processof this invention for providing a substantial yield of high molecularweight alkenyl substituted lactone reaction products in contrast toprior methods. The lactone reaction products of this process areparticularly effective as dispersants in motor fuel compositions.

I claim:
 1. A method for preparing a high molecular weightalkenyl-substituted lactone reaction product comprising the step ofadmixing an alkenylsuccinic acid, said alkenyl radical having an averagemolecular weight ranging from about 300 to 3,000 with a protonatingagent or electron pair acceptor selected from the group consisting ofsulfuric acid, perchloric acid, p-toluene sulfonic acid, borontrifluoride etherate and sulfonic acid ion exchange resins to form asubstantially anhydrous reaction mixture and reacting said mixture undersubstantially anhydrous reaction conditions at an elevated temperatureup to about 100° C until infrared spectra at about 5.66 and 5.74micrometers indicates a substantial conversion of said alkenyl-succinicacid to said lactone reaction product.
 2. A process according to claim 1in which the concentration of said protonating agent or electron pairacceptor is sufficient to provide from about 0.25 to 1.5 moles ofprotons or electron pair acceptors per mole of said alkenylsuccinicacid.
 3. A method according to claim 1 in which the concentration ofsaid protonating agent or electron pair acceptors is sufficient toprovide from about 0.5 to 1 moles of protons or electron pair acceptorsper mole of said alkenyl-succinic acid.
 4. A method according to claim 1in which the average molecular weight of said alkenyl radical rangesfrom about 700 to 2,000.
 5. A method according to claim 1 in which theaverage molecular weight of said alkenyl radical ranges from about 800to
 1200. 6. A method according to claim 1 in which said protonatingagent is concentrated sulfuric acid.
 7. A method according to claim 6 inwhich said protonating agent is 96 percent sulfuric acid.
 8. A methodaccording to claim 1 in which said reaction is conducted at atemperature ranging from about 60° to 100° C.
 9. A method according toclaim 1 in which said reaction is conducted at a temperature rangingfrom about 90° to 99° C.
 10. A method according to claim 1 in whichequimolar amounts of an alkenylsuccinic anhydride and water are reactedto form said alkenylsuccinic acid.
 11. A method according to claim 1 inwhich said reaction mixture is dissolved in an inert hydrocarbonsolvent.
 12. A method according to claim 11 in which said solvent is amineral oil.
 13. A method according to claim 1 in which infraredradiation absorption characteristics of lactone at about 5.61 and 5.74micrometers indicates the conversion of at least 50 percent of saidalkenylsuccinic acid to said lactone reaction product.
 14. A methodaccording to claim 1 in which said reaction mixture contains less thanabout 5 percent water.
 15. A method according to claim 1 in which saidreaction mixture contains less than about 2 percent water.
 16. A methodaccording to claim 1 in which said alkenyl radical has an averagemolecular weight ranging from about 1,000 to 3,000.
 17. A methodaccording to claim 13 in which the yield of lactones from saidalkenylsuccinic acid is greater than 85 mole percent.